Many current and future generations of communication devices, such as mobile handsets, ultra mobile devices (UMD) and laptop PCs (Personal Computer) have wireless transmitters and/or receivers of different communication technologies integrated into a single or same host device. These communication technologies may involve, for example, cellular radio technologies, such as GSM (Global System for Mobile communication), PCS (Personal Communications Services) and 3rd generation mobile radio technologies, as well as other communication technologies, such as WLAN (Wireless Local Area Network) and/or WiMAX (Worldwide Interoperability for Microwave Access) and/or DVB (Digital Video Broadcasting) radio technologies.
As a result of the international frequency assignments to which different communication devices must adhere, certain harmonics of certain cellular phone channels, for example, can fall into the channel in use in another receiver, such as a WLAN or WiMAX or DVB receiver. If the frequency bands of different technologies as such are not overlapping, it may still be that at least one harmonic frequency used in one radio technology falls into the receiving band of another radio technology. For example, the third harmonic of a GSM specific transmission frequency currently falls into a certain WLAN channel.
The interference caused by a transmitter to a receiver is understood to be narrowband interference if the majority of the interfering energy concentrates into a small sub-band which represents only a portion or a fraction of the total reception channel in use. For example, WLAN, WiMAX and DVB are wideband (or broadband) technologies using multi-carrier modulation and channel widths which are far broader than, for example, the bandwidth of a typical cellular transmission channel. Therefore, the basic cellular interference to these wideband systems may be considered as narrowband interference.
The source of interference, that is the interfering transmitter, may reside either in the same device which comprises the interfered receiver or in a separate device which is located nearby. Even when the source of interference resides in the nearby located device, the level of interference may be high enough to block the reception in the interfered receiver.